FIG. 8 of the accompanying drawings shows, in side elevation, a color cathode-ray tube partly in cross section. As shown in FIG. 8, the color cathode-ray tube has a tube body 101 including a funnel 101f and a panel 101p which has a fluorescent inner surface coated with color fluorescent materials. The panel 101p has an open end hermetically sealed against the open end of the funnel 101f by a glass frit 102.
The glass frit 102 is in the form of a liquid, i.e., a fluid when it is applied. FIG. 9 of the accompanying drawings shows the open end of the funnel 101f. As shown in FIG. 9, the glass frit is applied to the open end of the funnel 101f by moving a nozzle for ejecting the glass frit, from a position P, as a starting point, in the direction indicated by the arrow a, e.g., clockwise in FIG. 9. When the nozzle reaches the position P as an ending point again, the nozzle is stopped, thus coating the glass frit to the entire open end of the funnel 101f. If the starting and ending points of the nozzle overlap each other in the position P, then the coated layer of the glass frit is thicker in the position P than the coated layer in the other positions on the open end. If an effort is made to prevent the glass frit from being coated in overlapping layers at the starting and ending points, then the starting and ending points tend to be spaced from each other with no sufficient coating layer of glass frit therebetween.
In the event that the panel 101p is joined to the funnel 101f, as shown in FIG. 8, with the glass frit being thus applied, the hermetic seal may be impaired in the region where the glass frit is not sufficiently coated, and tend to develop a crack after the tube body is evacuated to a high degree of vacuum. When the tube body cracks, its reliability is reduced, e.g., it may explode or the degree of vacuum therein may be lowered.
In the event that the glass frit is excessively applied in overlapping layers, the glass frit is apt to squeeze out of joint between the funnel 101f and the panel 101p. Since the squeezed glass frit is responsible for the generation of dust in the tube after it is dried, it is necessary to remove the squeezed glass frit.
If the length of the open end of the funnel 101f, i.e., the length of a distance to be coated with a frit seal, is large as with a cathode-ray tube of a 45-inch size, it is highly inefficient for the nozzle to move all the way in a loop along the open end of the funnel 101f. One solution is to move two nozzles from a starting point P.sub.1 (see FIG. 10 of the accompanying drawings) along different paths, clockwise and counterclockwise as indicated by the arrows a, b, while applying a glass frit, and to stop applying the glass frit material from the nozzles at an ending point P.sub.2 that is positioned in symmetric relationship to the starting point P.sub.1. However, this coating process also suffers the above coating irregularities at the starting and ending points P.sub.1, P.sub.2.
It has been proposed to eliminate the above drawback with first and second nozzles 103, 104 as shown in FIG. 11A of the accompanying drawings, the first and second nozzles 103, 104 being closed with their open ends mating with each other. As shown in FIG. 11B of the accompanying drawings, when the nozzles 103, 104 are spaced from each other, they are opened to allow a supplied glass frit to flow or drop downwardly therefrom. The first and second nozzles 103, 104 are moved from the starting point P; (FIG. 10) clockwise and counterclockwise as indicated by the arrows a, b, while applying the glass frit. At the ending point P.sub.2, the open ends of the nozzles 103, 104 are closed, bringing the application of the frit to an end, as shown in FIG. 11A. In reality, the first and second nozzles 103, 104 are individually moved by independent robots, respectively. Because of limited mechanical accuracy or the like, it is highly difficult to hold the nozzles in accurate alignment with each other and close them at a desired position without a positional error, as shown in FIG. 11A. Even if this process is employed, the glass frit cannot actually be coated without irregular coating layers.
According to the present invention, there is provided a device for applying a fluid coating material, such as any of various adhesives, paints, or a glass frit material, uniformly and efficiently without coating irregularities, as when the funnel and panel of a cathode-ray tube body are joined to each other through such a fluid coating material.